Filaments having improved crimp characteristics and products containing same



June 19, 1962 v 1.. H. BELCK ETAL 9,524

FILAMENTS HAVING IMPROVED CRIMP CHARACTERISTIC AND PRODUCTS CONTAINING SAME Filed Nov. 3, 1958 2 Sheets-Sheet 1 FIG-1 -4 a r 2 l3 L 2 2 IO ll -42 INVENTORS LOTHA R HELMUT BELCK KARL GLENN SIEDSCHLAG, JR.

BY m A-A%'I'ORNEY ACTERISTICS DUCTS CONTAINING SAME L. H; BELCK E'TAL IMPROVED CRIMP CHAR Jime 19, 1962 Y 2 Shets-Shet 2 FILAMENTS HAVING AND PRO Filed Nov. a, 1958 FIG. 1

INVENTORS LOTHAR HELMUT BELCK KARL GLENN SIEDSCHLAG,JR. BY 3/1, ar 49247 ATTORNEY States -;Office 3,039,524 Patented June 19, 1962 3 039 524 FILAMENTS HAVING 'IM PROVED CRIMP CHAR- ACTERISTICS AND PRODUCTS CONTAINING SAME Lothar H. Belck, Waynesboro, Va and Karl Glenn Siedschlag, Jr., Wilmington, Del., assignors to du Pout de Nemours audCompany, Wilmington, Del., a corporation of Delaware Filed Nov. 3, 1958, Ser. No. 771,678 18 Claims. (CI. 28-42) at the same time, possessthe properties required to obtain fabrics of outstanding aesthetic appeal such, for example, as that which characterizes wool fabrics. Wool fabrics have good bulk and cover, obtainable at a relatively low finishing shrinkage which is quite desirable from an economic standpoint. In addition, wool fabrics have excellent elastic properties such as stretchability, compressional resilience, and liveliness, and display a pleasing surface handle. Finally, the surface of wool fabrics is renewable; even after such severe deformations as crushing or glazing, a new surface can easily be obtained for example, by wetting, steaming, or mere recovery in humid air.

Although different proposals of the prior art have attained one or more characteristics of wool fabrics, in no instance have such synthetic materials been properly considered as being wool-like in othe r than superficial appearance. For example, good bulk, cover, and surface softness have been obtained by 'processing into fabrics blends of fibers with'high and low residual shrinkage, and by subjecting the as-knit or as-woven fabrics to a shrinking treatment. Though the bulk and loft of fabrics prepared by this route are excellent, this improvement is at the expense of an undesirably high finishing shrinkage and resilience loss.

It has also been proposed to improve fabric aesthetics by imparting to the synthetic fibers a spiral crimp. Fibers of this type have been prepared by use of special spinning conditions or after-treatments which bring about differential physical properties over the cross-section of singlecomponent filaments, or by spinning together two or more materials to form a composite filament which contains the components in an eccentric relationship over the crosssection of the filaments; if the two components of a composite filament possess substantially different shrinkage, a crimp is caused by the differential shrinkage of the spun and drawn components. Such spirally crimped fibers, if embodied into fabrics, will impart a softer surface handle By use of such fibers and processes of the prior art, or combinations thereof, it has thus been possible to match or even to surpass wool in one or several aesthetic properties. But it has as yet not been possible to prepare synthetic fibers which duplicate wool aesthetics in all respects.

It is, therefore, an object of this invention to provide crimped filaments having improved response to textile finishing operations by virtue of reversible spontaneous crimp changes. It is a further object of the invention to provide filaments and yarns composed of such filaments which, when embodied into fabrics and subjected to finishing treatments, will develop bulk and cover at a low level of fabric shrinkage. A further object of the invention is to provide filaments and yarns of such filaments which, after processing into fabrics and finishing, will provide a yarn and fabric structure exhibiting improved stretchability, compressional resilience, and liveliness. A further object of the invention is to provide fibers which, when embodied in a fabric, will display a renewable surface. Further objects will appear hereinafter.

The objects of this invention have been attained by producing a crimped or crimpable composite filament of synthetically formed polymers in which at least one polymeric component has a substantial content of ionizable groups, preferably at least 30 milliequivalents of ionizable groups per kilogram of polymer in said polymeric component, said component also having combined in the polymer molecule a neutral or nonionic modifier (which, when incorporated into the polymer, increases the dyeability of fibers made therefrom with a disperse dye) said filament having the capacity of spontaneously changing its degree of crimp upon being exposed to the effect of a swelling agent and reverting to the original crimp upon removal of the swelling agent. This characteristic is, for convenience, referred to as crimp reversibility; general y speaking, this characteristic of the filaments of jthis'invention' is observed by the squirming of the filaand somewhat improved bulk without, however, providing ments upon both application and removal of the swelling agent.

The neutral modifier enhances the effect of the ionizable group content in that it either imparts to the filaments crimp reversibility which they would not possess in the absence of the neutral modifier or, alternatively, it improves crimp reversibility. vIn accordance with the invention, the enhancing effect of-the neutral modifier exhibits itself in composite filaments regardless of whether the ionizable roups of the component containing the neutral modifier are in excess of, less than, or the same as the ionizable group content of the other component of the composite fiber provided that the neutral modifier is present in its component polymer in an amount sufficient -to exhibit at least the minimum differential reversible length change, as compared with the other component, required, to induce crimp reversibility. The neutral modifier exhibits its enhancing effect even in small amounts,

e.g., 1% of the weight of the polymer containing the neutral modifier combined therein, but it is preferred that the neutral modifier be at least 3% of the weight of the polymer component in which it is combined.

The new improved filaments of this invention may be obtained by spinning together two or more critically selected synthetic polymeric materials, at least one of which is fiber-forming, in such a way that the materials form over the cross-section of the single composite filament two or more distinct zones which extend through the entire length of the filament in eccentric fashion,

whereby only one, or alternatively, part or all the components form the surface of the single composite filament. (For convenience, the following discussion will refer to two-component filaments although the filaments may, if desired, have more than two components.)

One component of the crimped filaments of the present invention displays a reversible length change, due to longitudinal swelling of the filament, to a substantially greater degree than the other component. By virtue of this characteristic, the crimp of composite filaments of this invention, upon exposure of the filament to a swelling agent, is, at least in part, altered but is regained upon removal of the swelling agent. The value of this crimp reversibility is evidenced by the ability of the filaments in yarns of this invention, when embodied in a fabric, to squirm or twist around in the fabric under the influence of a swelling agent such as water (and also on'removal of the swelling agent) but, nevertheless, to regain the original crimp in the fabric with removal of the swelling agent, as by drying. Fabrics containing these novel filaments acquire a high degree of fullness or covering power as a result of the swelling treatment and retain or even increase this fullness after being subjected to such treatments repeatedly. It will be understood that fabrics composed of the novel filaments can beneficially also be subjected to a physical working of the fabric to develop fullness and covering power to the greatest degree. Since the finishing shrinkage is low, the yarns of fabrics containing such filaments have a relatively open structure so that the fabrics exhibit unusual elastic properties. This reversible squirming crimp is also of particular advantage in pile fabrics such as those "used in carpets and upholstery where the compacting of 'the fibers under compression incident to use may be overcome; by treatment with water, other swelling agents, or merely exposure to humid air the fibers will squirm or work out of the compressed state but, upon drying, will again squirm and revert to their highly crimped and voluminous state which they had prior to being compressed. I

In order to develop the crimp reversibility characteristic of filaments of this invention, one component of the crimped filament should have a reversible length change by test A after shrinkage of at least 0.05% and preferably at least 0.10% more than that of the other component, that is, said component has at least 0.05% greater change in length of the original length upon swelling than the other component. The reversible length change of a component is determined by measuring the increase in length of a monocomponent filament of the component polymer (spun and subjected to after-treatments under the same conditions as the composite filament) upon being immersed in the aqueous medium used for the testing of the crimp reversibility of the composite filament.

For all reversible length changes denoted by test A the tests are executed with strands of approximately 100 denier and approximately 15 inches long as follows. The samples (previously relaxed by a boilolf) are clamped in a tensile tester with a small amount of slack and held in the proper medium (air, cold water, or hot water) for about 2 minutes. The mechanically driven clamp is then started at a low rate of elongation (0.3 inch per minute); it is stopped and reversed immediately when the stressstrain curve starts to depart from the zero line. The true length of the sample is then calculated from the clamp distance in the starting position and the chart distance between the start of the test and the point where the stress-strain curve began.

After wet tests the samples are dried (while clamped) by means of a hair dryer, and the length of dry strand at room temperature determined as above. Wet to dry cycles are repeated until the length change becomes constant. cycle. For most samples, satisfactory results are obtained with three cycles.

p 1.2 gram clamp. The sample is mounted vertically in a 4- The reversible length change is calculated in percent, based on the final dry length of the sample.

length Wet-length dry final length dry X 100 Results from at least four different strands are averaged to obtain a representative value.

A second test for equilibrium'reversible length change whose data is designated by testB was devised which gives results more reproducible than test A above, but which in general agrees with those results. In this test, strands of the drawn, unrelaxed continuous filaments are boiled in water for 15 minutes. Strands of approximately 300 total denier and 6 inches long are then suspended vertically from a rubber-tooth clamp and weighted with Reversible length change stoppered glass tube containing a desiccant in the bottom. The tube is stored vertically overnight (18-24 hours) at 70 C. After the 70 C. conditioning to dry the sample,

the 70 C. dry length, i.e., the distance between clamps,-

is determined with a cathetometer. The desiccant is then removed from the tube, the tube filled with water and stored vertically at 70 C. for 6 hours. It has been determined that all samples reachan equilibrium wet length at 70 C. in this period. The length of the wet sample is determined at 70' C. The cycles are repeated as required to obtain reproducible results.

One component of the crimped filament should have a reversible length change by test B after shrinkage of at least 0.4% and preferably at least 0.6% more than the other component in order to develop crimp reversibility.

If a component cannot be spun into a monocomponent I filament because its molecular weight is too low, its swell- As a rule some shrinkage occurs during the first ability is determined by extrapolation from the swellabilities of monocomponent filaments of the same polymer (in different spinnable molecular weights). v

In the processing of textile fibers and in the aesthetics of fabrics made from them, the level of crimp in the fiber is important. The proper level of crimp must be maintained in the fibers so that the fibers, in the form of staple fibers, will exhibit sufiicient coherence, at least during the early stages of yarn spinning operations, to permit their processing, e.g., combing, carding and drafting, in existing textile equipment as used in the trade for cotton, woolen and worsted spinning processes. Likewise, by adjusting the crimp, usually over the range of crimp which is processable, it is possible to vary fabric aesthetics. High crimp will produce bulky, lofty fabrics. Low crimp will produce consolidated, slick fabrics. This crimp, which is important to fabric aesthetics and fiber processability can be obtained easily if the two components of the fiber, in addition to the reversible length change difference discussed above, also exhibit a shrinkage differential.

To develop adequate crimp in the composite filaments, the shrinkability of one component should be at least 1% greater than the shrinkability of the other component, that is, said component has at least 1% greater loss of the Original length upon shrinkage than'the other component. The shrinkability of a componentis determined by measuring the shrinkage, upon immersion in boiling water under no tension, of a monocomponent filament made from the component polymer (spun and otherwise processed under substantially the same conditions as the composite filament). If a component cannot be spun into a monocomponent filament, e.g., because its molecular weight is too low, its shrinkability is determined by extrapolation from a graph of the shrinkage characteristics of monocomponent filaments of the same polymer (in different, spinnable molecular weights).

The filaments spun in accordance with this invention may be drawn, cross-linked, or subjected to other aftertreatments which may be desirable to improve the general properties of the fibers. When testing filaments of the individual components for reversible'length change or shrinkage, it is, of course, necessary that these are pre- '5 pared under the same spinning and after-treatment conditions as those used for the composite filaments.

The crimped fibers of this invention may contain helices which reverse direction at irregular intervals. Accurate measurements of crimp reversibility require samples without these reversals. Preparation of such filament samples was accomplished by a pretwisting of the filament (prior to exposure to the crimping medium) to the same degree as the crimp frequency found by'examination of similar filaments crimped without pretwisting. For crimp reversal measurements, the-pretwisted filament was crimped free of tension by immersion in boiling water or other suitable shrinking medium. The crimped filament was then suspended in a tube and kept from floating or bending by a small weight (1v milligram) attached to the lower (free) end and insufficient to remove crimp, the weight being pointer-shaped to permit measuring and counting rotationsof the pointer during crimping and uncrimping. The filament was treated successively to 5 cycles each consisting of a 5-minute exposure to 25 C. water followed by a -minute drying period in 25 C. moving air. The revolutions of the pointer (which are equivalent to the crimp changes) for the drying portion only of each cycle, were averaged for the 5 cycles and expressed as revolutions per centimeter of extended (straight) dry filament and are referred to hereinafter as crimp reversibility. Values from at least three filaments tested as above were averagedto obtain the crimp reversibility of a fiber. The crimp reversibility values were corrected to a four denier per filament figure which. can readily be done since crimp reversibility is inversely proportional to the cube root of denier. Crimp reversibility values by the above method are hereafter designated test A.

Again it was found that more reproducible crimp reversibility values were obtained under equilibrium conditions (corresponding to the reversible length changes by test B) than by the above test, although the same general results were obtained. Data measured by such an equilibrium test will be designated hereafter asfby test B. In this test a single filament is separated from the single end or tow of drawn, unrelaxed fibers. A three-inch length of the filament is attached to opposite sides of a rectangular copper wireframe with 30% slack between the ends. The rack and filament is then boiled off for minutes to develop the crimp. The crimped filament is then transferred to a special viewing holder by taping or gluing the ends so that about 10% slack is present and the filament length between the clamped ends is'approximately 2.5 inches. The filament and viewing holder is then mounted vertically in a stoppered test tube containing desiccant. The tube is stored vertically overnight (18-24 hours) at 70 C. Following this conditioning period to dry the filament the tube is then brought to room temperature (approximately 25 C.). After allowing 30 minutes for cooling the total number of crimps in the filament between the tfixed ends are counted. In counting, any crimp reversal points present are ignored. The desiccant is then removed from the glass tube, the tube filled with water and stored vertically at 70 C. for 6 hours. The number of crimps in the wet fiber are counted as above. The cycles are repeated as required to obtain reproducible results. The equilibrium crimp reversibility or change in crimps per inch of crimped length from 25 C. dry to 70 C. wet expressed as Ac.p.i. is obtained by the following equation where the sign of Ac.p.i. is ignored:

number of crimps (25 C. dry) number of crimps (70 C. wet) A total filament length crimped dry) ed together in the melt or solution but are fed separately to a shaped orifice where they are simultaneously extruded. The orifice is, then, adaptedto receive the components separately for simultaneous extrusion to form a are localized and held together in a side-by-side struc-- ture in which both components form part of the surface of the composite filament. The extrusion may also be such that one component forms a core and the other a sheath to form a compositereferred to hereinafter as a sheath-core structure. In this structure, only the sheath contributes to the surface ofthe composite.

The composite filaments are subjected to stretching, where applicable, and then given a shrinking treatment (to develop crimp) while substantially free of tension.

Referring to the drawings:

FIGURE 1 is a central cross-sectional elevation of a spinneret assembly which can be used to make the composite filaments of this invention;

FIGURE 2 is a transverse cross-sectional plan view of the apparatus of FIGURE 1 taken at 22 thereof and showing detail of the top of the back plate;

FIGURE 3 is a transverse cross-sectional plan view taken at 33 of FIGURE 1 showing details of the bottomof the back plate;

FIGURE 1A is an enlarged portion taken from FIG- URE l to show details of the spinneret at the spinning orifice; and

FIGURES 4, 5, and 6 show greatly magnified crosssections, i.e., sections perpendicular to the filament axis, of typical filaments of this invention produced by dry spinning. In these drawings one component is shaded to show the separation between components.

With reference to FIGURE 1, the bottom spinneret plate 2 which contains a circle of orifices 3 is held in place against back plate lby retaining rings 12 and 14 and by bolt 13. A fine-mesh screen 4 e.g., 200 mesh per inch, is

pressed into position between, and serves as a spacer between, spinneret plate 2 and back plate 1. Back plate 1 contains two annular chambers 8 and 9 which are connected to suitable piping and filtration apparatus (not shown) to receive different spinning compositions. Lead holes 11 go from annular chamber 9 to annular space 7. Lead holes 10 lead from annular chamber 8 to annular space '6. Annular spaces 6 and 7 are separated by wall 5 which" is disposed above orifices 3 and spaced from spinneret plate 2 by screen 4 to permit free and contiguous passage of the spinning fluids from annular spaces 6 and 7' through orifices 3, the mesh of screen 4 being fine enough to permit spinning lluid passage through orifices 3, as shown in detail in FIGURE 1A..

In FIGURE 2 are shown four lead holes 10 and four lead holes 11 equally spaced within the concentric chambers 8 and 9, respectively.

In FIGURE 3 are shown the concentric inner and outer annular spaces 6 and 7 and the fine-mesh screen 4 partially in section.

Operation of the described apparatus in the practice of this invention is readily understood. Separate spinning materials are supplied to the inner annular chamber 9 and outer annular chamber 8, respectively, of the back plate; the former flows from chamber 9 through the lead holes 11 into the inner annular space 7 and then through screen 4 and orifice '3 to form a part of a composite filament, while the latter passes through the lead hole 10 to the outer annular space 6 and thence through screen 4 and the outer side of the orifice 3 to form the other part of the composite filament.

The expression intrinsic viscosity" with the symbol 1; as used herein signifies the value of l'n(n),. at the ordinate axis intercept (i.e., when 0 equals 0) in a graph of as ordinate with values (grams per 100 ml. of solution) as abscissas. (n), is a symbol for relative viscosity, which is the ratio of the fiow times in a viscosimeter of a polymer solution and the solvent. In is the logarithm to the base c. All measurements on polymers containing acrylonitrile combined in the polymer molecule were made with dimethylformamide solutions at 25 C.

The acidity of a polymer was determined by percolatinga dimethylformamide solution of the polymer through an ion exchange column containing a mixture of a strongly acidic resin and a strongly basic resin followed by passage through a column containing the acidic resin alone. The free acid groups in the polymer solution were then titrated using an alcoholic solution of KOI-I and a suitable indicator. The polymer concentration was determined by evaporating a portion of the solution to dryness. Analytical results were expressed as milliequivalents of acidic groups per kilogram of dry polymer.-

The basicity of polymers was determined by dissolving the sample in cyclic tetramethylene sulfone, passing the polymer solution through a strongly basic ion exchange resin in the hydroxyl form and titrating with a solution of sulphuric acid in tctramethylene sulfone by a potentiometric method using a glass electrode. The polymer concentration was determined as set forth above with respect to the acidic polymer.

In the following examples, parts, proportions and percentages are by weight unless otherwise indicated. Also, in all the examples, the polymers were fed to the spinneret, in the form of their solutions, at an equal rate for each polymer so that the filaments contained 50% of each polymer. In addition, in those. examples referring to sodium styrene sulfonate, the sulfonate used was 92% sodium p-styrene sulfonate and 8% sodium o-styrene sulfonate.

Examples I, IA, IB and Example II (except for item B of Table 2) are, strictly speaking, not illustrations per se of the present invention. They are included, however, to describe methods for making and testing the polymers (including co-polymers) and the composite filaments used in the practice of this invention, to illustrate the effect of ionizable groups in the polymer components of composite filaments, and to indicate, by comparison, the efiicacy of neutral or non-ionic groups in imparting reversible length change and crimp reversibility to the filaments or in km proving these characteristics by enhancing the function of the ionizable group content of the component polymers of the composite filaments.

Item E of Example II and Examples III-VIII illustrate the preparation of composite filaments in which at least i one of the components has incorporated therein a nonionic dye enhancing modifier.

EXAMPLE I Copolymer (a) wasmade from acrylonitrile, methyl acrylate, and sodium styrene sulfonate using the technique of US Patents 2,628,223 and 2,546,238 (i.e., continuous polymerization in water with K S O catalyst, sodium meta bisulfite activator and 'Na CO for stopping the polymerization at the desired point) the monomers being fed to the reactor at relative rates of 93.63, 6.00, and 0.37%, respectively. The polymer had an intrinsic viscosity 1; of 1.5 and contained 54 milliequivalents of acid groups per kilogram of dry polymer. The polymer contained 6% of methyl acrylate. The proportion of methyl acrylate in a polymer has been found to be the same as in the feed monomers.

Copolymer ([1) was made in a similar manner from acrylonitrile and sodium styrene sulfonate with relative feed rates of the monomers of 97.0 and 3.0, respectively. The polymer had an intrinsic viscosity 1 of 1.5 and contained 204 millicquivalents of acid groups per kilogram of dry polymer.

Copolymer (c) was made in a similar manner from the continuous polymerization of a monomer feed consisting of 94% acrylonitrile and 6% methyl acrylate. The polymer had an intrinsic viscosity 1 of 2.1 and contained 26 milliequivalents of acid groups per kilogram of dry polymer which is considered to be present as acid end groups from the sodium meta bisulfite activator and the K S O used in the polymerization. The polymer contained 6.0% of methyl acrylate.

EXAMPLE I-A A 25% solution of copolymer (a) in dimethylformamide and a 25 solution of copolymer (b) in dimethylformamide were simultaneously spun in equal feeds as the two components of side-by-side filaments with a spinneret similar to that shown in FIGURES 1 to 3 having 18 orifices of 0.006 inch in diameter so as to extrude equal volumes of each component in each filament. The solutions were extruded at C. into an inert gas at 180 C. and wound up at 200 ypm after application of a spinning finish. The arrangement of the components in typical cross-sections resembled those of FIGURES 4 and 5. The spun yarn was drawn 300% (4X, i.e., to 4 times the length before drawing) in 95 C. water and dried.

Monocomponent filaments of each component polymer spun and drawn in the same manner as above had reversible length changes by test A of 0.46 and 0.64%, respectively, after shrinking and subjecting to the action of water at 25 C.

Equilibrium reversible length changes by test B of 3.67% and 6.51%, respectively, were observed.

EXAMPLE I-B Composite filaments were spun from 22% solutions in dimethylformamide of polyacrylonitrile (the homopolymer) with an intrinsic viscosity of 2.0 containing 26 milliequivalents of acid groups per kilogram of polymer and copolymer (0) through a spinneret similar to that shown in FIGURES 1 to 3 having orifices, 0.0047 inch in diameter, with other conditions as in Example I-A. The spun yarn was drawn 300% (to 4 times the original length before drawing) in steam. The as-spun filaments had cross-sections similar to FIGURES 4 and 5. Monocomponent filaments of the component polymers, spun and drawn in the same manner, had reversible length changes by test A of 0.19% and 0.16%, respectively, after shrinkmg.

Equilibrium reversible length changes by test B of 1.0 and 1.3% were measured.

Samples of both drawn composite yarns A and B developed approximately 20 helical crimps per inch of extended fiber length (i.e., with the crimps pulled out) respectively, in boiling water. The crimped filaments had crimp reversibilities by test A of 0.11 and 0.0 crimp per centimeter, respectively, for samples A and B.

Equilibrium crimp reversibilities by test B of 4.5 and 0.40 crimps per inch change were obtained. The value of the wet initial modulus (Mi) is directly related to the work that the crimped fiber can do in the crimp reversing step between the wet state and the dry state. Initial values (25 C. wet) were 20 and 23 grams per denier (g.p.d.) for samples A and B, respectively.

Tufted (pile) fabrics of similar construction were made from the 3-denier per filament unrelaxed (uncrimped) filaments of Example I-A, Example IB, and homocomponent filaments of copolymer (a). The fabrics were boiled in water for 30 minutes, air-dried, and brushed up with a hand card. Each pile fabric was then crushed for 24 hours to 10 to 20% of its initial height by a 1 kilogram weight 2 inches in diameter. After the weight was removed, the fabric was allowed to stand in air of approximately 60% relative humidity for 24 hours. The fabric was then immersed in 60 C. water for 1 minute without agitation, and air-dried. The fabric from homocomponent filaments showed no recovery after any of the treatments. The fabric from the filaments of Example I-A (having crimp reversability) recovered about 90% of its original height after-24 hours and recovered 100% after the wetting and drying cycle. The fabric from the filaments of Example I-B (no crimp reversibility) showed no dry recovery and only about 30% recovery after wetting anddrying.

Staple fiber (70 parts),was cut from thefilaments of Example: I-A and blended with wool (30 parts) spun into yarn, woven into a Shetland-type fabric and subjected to the usual finishing and fullingroperations employed for wool fabrics of this type. The finished fabric was equivalent to a similar all-wool fabric in bulk and cover, in the low shrinkage experienced during the fabric finishing steps (e.g., 25-and shrinkage in the warp and fill directions, respectively) in'elasticity and liveliness, and in the soft, pleasing wool-like surface handle. Similarly con structed fabrics of synthetic filaments not having crimp reversibility displayed poor bulk and cover despite higher shrinkages, poor elastic properties, and had a less woollike surface handle.

An additional demonstration of the useful properties of the filaments of this invention was made by measuring. the recovery of the fibers from compression. Crimped. fibers were cut in 2-inch lengths, hand carded and madev into pellets weighing 0.30 gram.- The pelletswere placed into a cylinder (0.5 inch diameter hole) under a freely sliding piston that exerted 1,000 p.s.i-. for two minutes. Theheight of the pellet under compression was measured. Different compressed pellets ofthe'same fiberwere: (I) allowed to recover in dry air 4 hours or (2) placed in C..water for 40 minutes to recover. The heights of the recovered pellets after treatments 1 and2' were then measured. Results with the composite filaments in-E-xamples I-A, I-B, and the homocomponent filaments of copolymer (c) are given in-the next Table as items A, B, and C, respectively.

Table I PELLEP HEIGHT, IN INCHES Recovered Compressed dry, 4 hours Recovered cold-wet, 40 minutes Item The monomers, ac rylonitrile AN (e), methyl acrylate MA (1), sodium styrene sulfonate'SSA (g), methacrylic acid MAA (h), and acrylamide AC (1') were used to make polymers and copolymers in an aqueous continuous polymerization, as in Example I, using monomer feed ratios as shown in Table 2 which follows later herein. The resulting polymers were used to make crimped composite filaments, as in Example I. Monocomponent filaments were made in a similar manner from the polymer components of the composite filaments.

Examination of the data on items A, B, and C in Table 2 which follows later herein, clearly shows the importance of the difference in ionizable group content between com ponents as demonstrated here by sulfonic acid groups in causing a reversible, length change in water and the corresponding effect upon crimp reversibility in the compositefilament. Item D demonstrates the beneficial use of an acid modifier other than styrene-sulfonic acid in producing a reversible crimp in a filament.

A The spun yarn of item B was cross-linked 'beforedraw-v ing by treating the spun yarn wound on perforated tubes in a solution composed of 50 gallons of water, 3 gallons of 40% formaldehyde, and 3 pounds ofv concentrated sulfuric acid for 18 minutes at 98 C. The cross-linked fiber was then drawn 4 in a 0.3% sodium carbonate solution at C. The drawn fibers were then boiled for one hour on perforated tubes in 0.5% NaI-ICO They were then cut into two-inch lengths and boiled for one hour in distilled water, which developed a very excellent spiralcrimp (designated salt in Table 2 which follows later herein). Another portion of the drawn yarn was boiled free of tension in 1% hydrochloric acid for 30 minutes followed by boiling in water to obtain the crimp (designated acid in Table 2).

It is considered that cross-linking is merely a means of obtaining the proper balance of physical properties between the components of the composite filament.

All of the above composite filaments displayed equal or superior dryv and wet recovery from compression to that of the filaments of Example I-A using the pellet test of Example I.

EXAMPLE III alents of basic groups per kilogram of dry polymen,

Solutions of this polymer and polyacrylonitrile (the homopolymer) of n 2.0 containing 22% polymer in dimethylformarnide were dry-spun, as in Example I-B, andthe resulting yarn drawn 4 in 95 C. water. Boiling the unrestrained yarn gave a very excellentlycrimped product with 20 crimps per extended inch with properties as shown under item F in Table 2.

EXAMPLE IV A copolymer (component I) containing 4.7% of.

methylacrylate and 176 milliequivalents per kilogram of acidgroups with an intrinsic viscosity 1 of 2.0 was made from, acrylonitrile, methyl acrylate, and sodium styrene sulfonate'using the technique ofExarnple I.

A. second copolymer of an intrinsic viscosity 1; 2.0 containing 180 milliequivalents of acid groups per kilogram and no methyl acrylate groups was made from acrylonitrile and sodium styrene sulfonate using the polymerization technique of Example I. The two polymers were co-spun as in Example III and the resulting composite filaments drawn 4 in 95 C. water. Relaxation in boiling water gave an excellent crimped product with properties as described under item G in Table 2.

It was very surprising that the presence of the methyl acrylate in the polymer component having the lesser acidity so enhanced the effect of the ionizable groups present in component A that it had a greater reversible length change than the other component and hence caused a reversible crimp.

EXAMPLE V A copolymer (component I) was made from acrylonitrile, N-vinyl pyrrolidone NVP (l), and sodium styrene sulfonate using the technique of Example I.

A second copolymer was made from acrylonitrile and sodium styrene sulfonate. The two polymers were cspun as in Example III and drawn 8x. Relaxation in boiling water gave good crimped filaments with properties as described under item H in Table 2. The presence of the N-vinyl pyrrolidone units so enhanced the ionizable groups in component I that it had a greater reversible length change than the other component and caused a reversible crimp.

The above polymers can also'be spun into side-by-side types of composite filaments.

Tubing knitted from the above yarns showed a considerable increase in bulking and covering power over control tubing from the polyester homofilaments. Ribbons made with the sheath-core yarns as filling exhibited a much softer hand after boil-off thanv did those with all homofilament yarns.

The effect of the acidic group in a component is en- Table 2 Monomer feed ratios Polymer acidity 1 milliequivalents/kg.

Item

Component I Component II I II I-II e/g (AN/SSA), 95/5 e (AN) 346 28 318 e/g (AN/SSA), 97.25/2.75. e/g (AN/SSA), 98 75/1 25 274 141 133 e/g (AN/SSA), 97.5/2.5 e/g (AN/SSA), 98 ll 5 189 132 57 e/f/ (AN M A/SSA 93 6816/.37 c/h (AN/MA. 54 550 -490 ell/t1 (AN/MA/S 550 54 496 e (AN) 380 26 354 elf/g (AN/MA/SSA), 92.5/ e/g (AN/SSA), 97.2/2.8 176 180 4 ell/g (AN/NVP/SSA), 88. e/g (AN/SSA), 98/2 144 160 14 IIomocomponent Composite filaments filament reversible S (I-II) length change, Draw Item percent ratio Den/til. Crimp reversibility Crimp Modulus per ex. 25 wet inch Test A-I Test A-Il Test A Test B Test A Test B 0.71 0.19 52 4. 3 8X 6 35 0.73 13. 2 30 0. 56 0. 27 29 1. 8 8X 2 26 0. 17 8.2 25 0.38 0. 26 .12 0.6 8X 3 29 0.09 2. G 0. 46 0. 99 53 3.0 4X 3 19 5 4. 4 4X 3 50 0. 8 12.5 52 salt 0.7 47 acid 1 0. 30 0.19 l1 4X 3 23 1 0.3 1 5. 7 20 1. 23 0. 69 0. 54 0. 8 8X 3 21 0. 48 4. 0 20 8X 0.9 49

l Basieity. 2 At pH 3. Orimps per crimped length.

Norn.-Both components of all items had (1;) of 2.0 except D and E which had (1:) of 1.5.

EXAMPLE VI A series of copolyesters containing sulfonic acid side groups were made by copolymerizing sodium 3,5-di(carbomethoxy)benzene sulfonate (DCBS) with dimethyl terephthalate and ethylene glycol by ester exchange. These copolyesters were melt. spun as the sheath of a composite filament around eccentrically disposed cores of poly(ethylene terephthalate) containing meq. of carboxyl groups per kg. of polymer with a relative viscosity of 24.6 using a spinneret similar to that shown in copending and coassigned application S.N. 519,031 filed June 30, 1955, to J. Kilian, now US. Patent 2,936,482. All yarns (34 filaments) were drawn over a hot pin at about 104 C. Physical properties were determined on dry yarns after boiling in waterfor minutes in a relaxed condition. The results are shown in Table 3 which follows.

Table 3 Sheath compo nent Shcath/ Crimps/ Crimp core inch of reversi- Item weight Denier Draw crirnped hility Moi. Acidity ratio ratio length ACPI percent meq./

BS kg.

hanced by the incorporation of a neutral modifier in the polymer as by replacing a portion (3 to 10% by weight) of the ethylene glycol with a poly(ethylene oxide) glycol of molecular weight 6000 in the polymerization.

EXAMPLE VII This example illustrates how suitable components may be selected for use in the composite filaments of this in vention.

Various copolymers of acrylonitrile were prepared, as in Example I, spun into homocomponent filaments and the pertinent properties measured. These results are given in Table 4 which follows. Reversible length changes were determined in 25 C. water for test A and also under conditions of test B. In general, it will be noted that as the ionic groups content at constant neutral modifier content, of a polymer increases, the reversible length change of yarn prepared from it increases.

Items 3 and 4, 5 and 6, and 9 and 1-0 expressly show the effect of neutral modifier on reversible length change of the filaments. Items 18 and 19 show the reversible length change obtained with basic groups in an acid swelling medium.

The data of this example shows a process variable that changes the reversible length change of the filaments, namely, the draw ratio. As the draw ratio is increased for a given polymer, the reversible length change is decreased. This data indicated the importance of examining homofilaments of prospective polymer candidates for the com- 13 posite filaments of this invention, under the same conditions that they are to be spun, drawn or otherwise treated in the resulting composite fiber.

towards shrinkage. The boil-off strips were then suspended I freejof weights over a hot plate to dry. During the drying process the films formed a spiral crimp. This crimp Table 4 Polymer Filaments Monomer Monomers feed ratio Draw Revers- Length Shrink- Mi-wet (17) Acidity. ratio this change age 25 C Test A Test B 1. 2. 26 0. 97 2. AN/MA.-- 2.0 27 1.30 3. AN/MA/SS 1. 70 3.4 4. AN/SSA... 1. 5 80 2.8 5. AN/MA/SSA- 1. 5 130 4.8 6. ANISSA 1.5 130 3.9 7. N SSA 2.0 98 1. 57 41 g 2. 3 17s 0. a. 65 21 23 9, 2. 3 176 1. 7. 90 32 15 10. 2. 0 204 0. 6. 51 29 11. 2. 0 204 0. 3. 00 17 27 12, 2.0 346 0. 5. 05 21 16. 5 13, 1. 15 550 0,- 6. 56 34 16 14. 1.2 535 0. 7. 58 28 20 15. 1. 1 384 4.02 26 19 16. 1. 5 0. 2. 62 28 28 17, 1. 9 157 0. 3. 67 22 23 18. 1. 7 5 318 a 0. 8 1. 69 24 18 19. 1. 7 2 318 4X 3 0.25 3 1.11 23 22 NOTE.AN=3.CrylOI11tri1e, M'A=mcthyl acrylate, and SSA=sodium p-styrene sulfonate.

EXAMPLE VIII Another means of evaluating polymer candidates for use in the composite filaments ofthis inventionis by means of cast films using known techniques. Polymers can be quickly and readily cast into films, cut and then carefully drawn, relaxed, and shrinkage measurements and thereafter differential length change measurements made thereon. Composite films can be made by casting one'polymer solution upon another.

Various polymers and copolymers were made from acrylonitrile, sodium styrene sulfonate, methyl acrylate and 2-vinyl pyridine using the polymerization techniques of Example I. These polymers were then blended as desired to give the required content of ionizable groups and of methyl acrylate. The component polymers for items A, B and C, as shown in Table .5 which follows, were all acrylonitrile copolymers as made. The polymers for items D, E and F of Table 5 were made by blending a copolymer with either the homopolyrner of acrylonitrile or with a copolymer of acrylonitrile and methyl acrylate (94/6 weight ratio. The intrinsic viscosity 1; of all polymers and blends were 2.0 with the exception of the parent acrylonitrile/ vinyl pyridine polymer which had an intrinsic viscosity 1 of 1.35. a

The various polymers and blends were each dissolved in dimethylformamide to make a 15% solution of the polymer. A film was cast from a polymer solution on a glass plate by means of a doctors knife having a clearance of 0.010 inch. This film was dried for minutes at 95 C. in a forced draft oven. An equal amount of a second solution was then cast over this film in a similar manner to yield a final film having of each polymer, andthe composite film was then dried under the same conditions as the first film except that it was dried for one hour. The composite films were stripped from the plate, cut into A; inch wide strips and drawn 4X over a pin heated to was completely reversible in that when the crimped, dried, composite films were placed in water and allowed to come to equilibrium they straightened out spontaneously and upon drying again reverted to the crimped condition. It is considered that this crimp represents the crimp reversibility that is due to the difierential length change of the two components. It was surprising that a crimped product could be made in the absence of a difierential boil-01f shrinkage between the two components.

The results with, various combinations are shown in Table 5. Items A and B of Table 5 have been included to demonstrate the validity of this method of testing for components inasmuch as these types of pairs of components had already been evaluated in fiber form and gave the same results.

Table 5 Composite film, Component A Component B crimps per 1extended 1110 Item I Percent Acidity 1 Percent Acidity 1 Reversmethyl meqJkg. methyl meq./kg. Total ible aerylate acrylate erimps l Acidity from sodium styrene sulionate and acid end groups. iasugt g (from 2vinyl pyridine).

The data indicate that when there is no dilference in ionic ionizable group content between the two components at levels as low as 50 milliequivalents per kilogram the presence of 5% methyl acrylate in one component makes that component have a sufiiciently higher reversible length change, so that a composite fiber with reversible crimp can be made from that pair of components.

Item F indicates the effect of methyl acrylate on a basic-modified polymer.

Either component of the composite, crimp reversible filaments of this invention can be found in the class of polymersv consisting of synthetic addition polymers and linear polyesters.

Among the polyesters that may be mentioned, besides poly(ethylene terephthalate) are the corresponding copolymers containing sebacic acid, adipic acid, isophthalic acid as well as the polyesters containing recurring units derived from glycols with more than two carbons in the chain, e.g., diethylene glycol, butylene gIycoL decamethylene glycol and trans-bis-l,4-(hydroxymethyl)-cyclohexane. Polymers derived from acrylonitrile and particularly those containing 80% or more of acrylonitrile combined in the polymer molecule are particularly useful in the practice of this invention. Polymers containing 80% or more of acrylonitrile combined in the polymer molecule, i.e., both the homopolymers and copolymers, are especially preferred in the practice of this invention because of the chemical inertness, general water insensitivity, high modulus, high tensile strength, light and weather stability and especially the pleasing handle, etc. that are characteristics of filaments formed from these polymers. In general, both components will be preferably made of similar polymers, e.g., both acrylonitrile poly-. mers in order that optimum adhesion be obtained between the two components. The necessary difierential reversible length change between the components is readily obtained by selecting the content of ionizable groups in the two polymers and the amount of neutral modifier.

Such ionizable groups are readily obtained by copolymerizing acrylonitrile, for example, with monomers containing acid groups such as carboxylic, sulfonic or phosphonic in either the salt or free-acid form.

Among the carboxylic monomers suitable for use in this invention are: acrylic acid, alpha-chloroacrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, citraconic acid, crotonic acid, vinyl benzoic acid and the like.

The use of stronger (i.e., more highly ionized) acid groups as sulfonic or phosphonic acids, as for example, l-propene-Z-phosphonic (see U.S. Patent No. 2,439,214) or phenylethene-Z-phosphonic acids are preferred in this invention since they are, in general, more effective than carboxylic acids in causing a reversible length change and also because their copolymers are substantially more stable to heat discoloration.

In addition to p-styrenesulfonic acid, methallyl sulfonic acid, allyl sulfonic acid and ethylenesulfonic acid disclosed above in this application, the following sulfonated polymerizable monomers and their salts are eminently suited for use in this invention: and mstyrenesulfonic acid, allyloxyethylsulfonic acid, methallyloxyethylsulfonic acid, allyloxypropanolsulfonic acid, allyl thioethylsulfonic acid, allylthiopropanolsulfonie acid, isopropenylbenzenesulfonic acid, vinylbromobenzenesnlfonic acid, vinylfluorobenzenesulfonic acid, vinylmethylbenzenesulfonic acid, vinylethylbenzenesulfonic acid, isopropenylisopropylbenzenesulfonic acid, vinylhydroxybenzenesulfonic acid, vinyldichlorobenzenesulfonic acid, vinyldihydroxybenzenesulfonic acid, vinyltrihydroxybenzenesulfonic acid, vinylhydroxynaphthalenesulfonic acid, isopropenylnaphthalenesulfonic acid, sulfodichlorovinylnaphthalene, allylbenzenesulfonic acid, methallylbenzenesulfonic acid, isopropenylphenyl-n-butanesulfonic acid, vinylchlorophenylethanesulfonic acid, vinylhydroxyphenylmethanesulfonic acid, vinyltrihydroxyphenylethanesulfonic acid, 1-isopropylethylene-l-sulfonic acid, lacetylethylene-l-sulfonic acid, naphthylethylenesulfonic acid, biphenyloxyethylenesulfonic acid, propenesulfonic acid, butenesulfonic acid, hexenesulfonic acid, etc. Salts of di-acids such as of disulfonic acids may also be used, for example, salts of 3,4-disulfobutene(1), vinylbenzenedisulfonic acid, vinylsulfophenylmethanesulfonic acid, allylidinesulfonic acid, etc.

Sulfonic acid groups can be introduced as end groups in polyesters by using metallic salts of sulfomonocarboxylic esters such as sodium p-carbomethoxy benzene sulfonate and dipotassium S-carbomethoxy benzene-1,3- disulfonate and sulfomonohydric alcohols, such as sodium-3-hydroxy propane-l-sulfonate as chain terminators.

Sulfonate acid groups can be placed in mid-chain units of a polyester by using as a monomer, a dicarboxylic acid compound or its derivative containing a metallic salt of a sulfonate, such as sodium l,8-di(carbomethoxy)- naphthalene 3-sulfonate, potassium 2,5-di(carbornethoxy)benzene sulfonate, and sodium 4,4-dicarbomethoxy butane-l-sulfonate.

Carboxy groups and their salts in a polyester are also useful in this invention although sulfonic acid is preferred. They can be introduced as end groups by using an excess of a dibasic acid or by degrading a polymer by various means. Chain terminators such as potassium monomethyl terephthalate, potassium hydroxybutyrate, or potassium monomethyl sebacate can be used in ester exchange polymerizations.

Car-boxy groups can also be introduced to mid-chain units of a polyester. Metallic salts of carboxylic acids do not enter into an ester exchange polymerization, so that compounds such as potassium dirnethyltrimesate, or the potassium salt of desoxycholic acid can be copolymerized with, for example, dimethyl terephthalate. Mid-chain carboxy groups can also be introduced by melt blending a polyester having predominately hydroxyl end groups with a dianhydride such as pyromell-itic anhydride followed by extrusion of the modified polyester into shaped articles, the holding time at the high temperature of melt-blending and extrusion being of short duration.

The required ionizable groups can also be obtained by the use of basic comonomers, such as Z-vinyl pyridine, 2-methyl-5-vinyl pyridine and others of that type [as disclosed in 2,491,471, issued to Arnold, p-dimethylaminomethyl styrene (see U.S. Patent No. 2,691,640) vinyl ethers of amino alcohols such as betadiethyl aminoethyl vinyl ether, esters of acrylic and methacrylic acid with amino alcohols such as N,N-diethy1aminoethyl acrylate, and polymerizable quaternary ammonium compounds, such as allyltriethylammonium chloride, vinyl pyridinium chloride, allylpyridinium bromide, methallylpyridinium chloride, and others as disclosed in Price U.S. Patent 2,723,238 issued November 8, 1955, betavinyloxyethyl dicarbomethoxyethyl methylammonium chloride and others as disclosed in Albisetti and Barney, U.S. Patent No. 2,729,622 issued January 3, 1956, and others. The use of polymerizable quaternary ammonium compounds as sources of basic ionizable groups in the polymers of the filaments of this invention are preferred over other basic modified polymers due to their higher basic strength.

Although the polymers containing basic groups are preferably made by copolymerization, it will be obvious to those skilled in the art that such basic groups can arise from the after-treatment of the polymer or of the fiber, as for example, the reduction-arnination of polymers containing ketone groups made from much monomers as methyl vinyl ketone, isopropenyl methyl ketone and the like as disclosed in Ham U.S. Patent No. 2,740,763 issued April 3, 1956, or by the quaternization of a nitrogen group in a solution of a copolymer, such as a copolymer of acrylonitrile and 2-vinyl pyridine as shown in Ham U.S. Patent No. 2,676,952 issued April 27, 1954, or by exposure of a copolymer containing a methallyl haloacetate to quaternization conditions in a spinning solution as disclosed in Ham U.S. Patent No. 2,656,326 issued October 20, 1953.

It will be obvious to those skilled in the art that the required ionizable groups can be incorporated into a polymeric component by blending of 2 or more polymers. The polymers should preferably be compatible.

The use of acidic modifiers in a copolymer are preferred since in general they afford better polymerizations, such as less tendency to form insoluble gels than basic modifiers. Polymers, their spinning solutions and spun fibers containing acid groups (especially sulfonic) are more resistant to discoloration by heat than are the basic modified polymers. Such acidic modified polymers also permit cross-dyeing with wool fibers since the wool takes -required reversible length change.

acid dyes and the acidicmodifying groups take basic dyes. taining aminegroups is that such amine groups must be in a salt form to ionize, which requires an acid pretreatment or an aqueous, acidic swelling medium. In this connection, it will be understood that ionizable groups are those which ionize in the swelling mediumto-which the filaments are subjected. This medium is normally an aqueous medium which is substantially neutral, but in some cases as where aminesalt groups represent the ionizable groups, the swelling medium may bean acidcontaining aqueous medium.

It will be apparent to those skilled in the art that vinyl polymers other than acrylonitrile polymers-can be used in this invention which, although not having the be modified by acidic or basic modifiers and neutral modifiers as suggested above, so that the copolymers do have the In this manner such vinyl monomers as vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ketones, vinyl ethers and various acrylic esters and their copolymers, can be used in the required reversible length change per se, can

An additional disadvantage of the polymers conlents, of ionizable groups per form of their copolymers with the acidic or basic modifiers, as components of the filaments of this invention. One example of one such modified vinyl polymer-having an ionic modifier togetherwith non-ionic modifier can be prepared as follows:

A copolymer of vinyl chloride and vinyl acetate (5% by .weight of copolymer) containing 200 milliequivalents of p-styrenesulfonic acid per kilogram of polymer is made by using the polymerization technique of US. Patent. No. 2,628,957. A solution of this polymer in tetrahydrofurane is co-spun, as in Example I above. with a 25 solution of the homopolymer of polyvinyl chloride in tetrahydrofurane and then drawn4 in. 98 C. water. The composite fibers display a crimp. reversibility after shrinking in boiling water superior to that made withoutv the vinylacetate but containing thesame p-sulfoni'c acid content.

It was surprising that the inclusion of from 1-15% of certain non-ionic modifiers in copolymers of acrylo nitrile enhanced the effect of any ionizable groups present in the final polymer. It is considered that these neutral monomers which enhanced the effect of the ionizable groups can be considered asbelonging to one of two classes: I

(1) Hydrophobic-polar monomers, i.e.,. waterrinsoluble monomers which contain a esters, ketones or amides;

(2) Hydrophylic monomers, i.e., those that are watersoluble such as acrylamide andrnethacrylamide.

In general, it has been found that the monomers that are etfective in this connection are also the same monomers which, when incorporated into an acrylonitrile polymer increase the dyeability of fibers made therefrom with a disperse dye, such as the blue-disperse dye Prototype 62. also be afiected, but the eliect of the neutral monomer-s is more readily seen by the use of a disperse dye alone.

Among the more desirable. monomers from the point. of view of enhancing the efiect. of ionizable groupv content are methyl ,acrylate, methyl. methacrylate, methyl vinyl ketone, .acrylamide, N-tertiarybutyl acrylamide, vinyl methoxyethyl ether, methoxyethylacrylate, vinyl acetate, bis(2-chloroethyl) vinyl. phosphonate, N-vinylpyrrolidone, N-vinyl,N-methylformamide and N,N-dimethyl acrylamides Suitable monomers may be found among ethyl methacrylate, butyl methacrylate, octyl methacrylate, methoxyethyl methacrylate, phenyl methacrylate, cyclohexyl, methacrylate, dimethyl amidoethyl methacrylate, and the corresponding esters of acrylic acid; acrylamides and methacrylamides or alkyl substitution products thereof; unsaturated ketones such as phenyl vinyl ketone, methyl isopropenyl ketone and the like; vinyl carboxylates such carbonyl group such as Dyeability with acid or basic dyes-may 18 as vinyl formate, vinyl propionate, vinyl butyrate, vinyl thiolacetate, vinyl benzoate, esters of ethylene alpha, betacarboxylic acids such as maleic, fumaric, citraconic, mesaconic, aconic acids, N-vinyl succinimide, vinyl ethers, etc.

While the inclusion of as. little as 1% of one of the above monomers enhances the reversible length change efiect of the ionizable groups contained in that polymer,'generally from 3 to 10% is desired. Although a further slight enhancement is obtained as the concentration is increased above 10%, usually the mechanical properties of the fibers sutfer at undueheights of polymer modification so that in any event for the case of the acrylonitrile polymers no more than 15% of the neutral modifier should be used.

The composite filaments of this invention are characterized in that at least one of the components contains a substantial amount, preferably at least milliequivakilogram of polymer and a substantial amount of neutral (disperse dye enhancing) monomer. One component, in addition to containing at least 30 milliequivalents, may contain a substantial excess of ionizable groups over the other component. The

non-ionic or neutral disperse dye enhancing monomers disclosed herein increase the eifect of the ionizable groups in said component in proportion to the concentration of the non-ionic modifier.

The .patent application of Robert Burns Taylor, Jr.,

. Serial No. 771,677, filed of even date herewith is concomponents,

cerned with the selection of components, such that at least one component contains at least 50 milliequivalents per kilogram of polymer of ionizable groups and preferably one component contains at least 50' milliequivalents per kilogram of polymer of ionizable groups in excess of those contained by the other component. The present invention is concerned with the improvement caused by the presence of a neutral disperse dye-enhancing modifier in one component, so that that component has the greater reversible length change upon swelling and deswellin g.

The following invention: I

1) "A greater differential reversible length change between components and hence a greater crimp reversibility in the co-fiber is obtained in a pair of given A and B, when component .A having (1) an excess of ionizable groups over B, (2) a greater reversible length change, and (3) containing no disperse dye-enhancing monomer is replaced by a polymer with the same ionizable group content and containing a substantial' amount ofa disperse dye-enhancing modifier.

(2) Pairsv of components, neither of which contains a disperse dye-enhancing modifier, not having a sutficiently high differential reversible length change'to afcord crimp reversibility (in a co-fiber) can be modified by the presence of a sutficient amount of disperse dyeenhancing modifier in one component to give the required reversible length change.

It: is to be understood that any convenient levelof modification by monomers having ionizable groups and by non-ionic disperse dye enhancing monomers can be selected in 'view of other desiredattributes of such modification such as, for example, dyeability.

Theselectionof the components to be incorporated into 'the composite fibers will depend on the physical properties desired of the filaments and yarns, e.g., the optimum residual shrinkage, tensile recovery, elongation, such as desired for textile filaments, and the like, that is, properties being readily determined by known methods. Physical properties of the desired components,

taken alone, can be relied upon for the selection of the 4 preferred that the wet modulus at 25 C. of both comsituations are comprehended by this 19 ponents be at least g.p.d. -A selection of a high reversible length change difference together with high wet modulus for both components contributes greatly to the irnpelling force responsible for the high crimp reversi bility characteristics of the filaments of this invention. The product of the'ditference of reversible length change by test A (in percent) between the components multiplied by the 25 C. wet initial modulus (in g.p.d.) of the composite filament is preferably at least 2.0.

Composite filaments prepared for use in accordance with the present invention may be subjected to a drawing (permanent stretching) operation in order to impart to the filaments the desired physical properties as tenacity, elongation and initial modulus. Although drawing may affect shrinkability and the reversible length change of a filament, crimped filaments with a reversible crimp have been made from dry-spun filaments without a drawing treatment. The conditions applied to drawing the spun multicomponent filaments may vary in wide limits. The drawing characteristics of the components can readily be determined from those of monocomponent filaments of each of the component polymers of the composite filaments. The drawing can be accomplished in accordance with known principles applicable to the particular polymers of the composite filaments and, in general, the composite filaments are drawn at least 50% (i.e., to 150% of original undrawn length) and preferably about 2-8 times the original lengths. The extent of drawing will, of course, also depend somewhat upon the nature of the particular polymer used in the composite filaments and upon the type of eccentric relationship between those polymers in the composite filament.

In considering the extent of drawing, one should take into consideration the amount of draw which may be effected during the spinning of the filaments, and, in fact, the desired amount of drawing may be effected during spinning rather than as a separate drawing step following the windup of the filaments from the spinning operation.

The shrinking of the composite filaments in order to effect crimping, may be carried out by the use of any suitable known shrinking agent. Shrinking will ordinarily be carried out by the use of hot aqueous media such as hot or boiling water, steam, or hot highly humid atmosphere, or by the use of hot air or other hot gaseous or liquid media chemically inert to the polymers of the composite filaments. The shrinking temperature is generally in the neighborhood of 100 C. but may be higher or lower, e.g., 50 C. up to about 150 C. or even up to a temperature not exceeding the melting point of the lowest melting polymeric component of the fiber.

A continuous process for the production of the crimped filaments of this invention is a follows: The tow of spun yarn is washed of residual solvent and simultaneously drawn 4X in 95-98 C. water followed by an additional draw of 2X (total draw 8X) through a steam cell in 20 psi. (gage) of steam. The drawn yarn is piddled (deposited transversely and lengthwise of a traveling belt as described in U.S. Patent No. 2,333,279) from the steam cell and cut into staple lengths with a rotary knife cutter. The cut chips of staple are sprayed with water to a minimum of 50% water content and then steamed and dried in sequence on a conveyor, which treatment crimps the fibers. The dried chips are then opened and baled.

If a less intense crimp is desired, the cut chips may be dried, e.g., with 90 air, opened and then crimped by heating with, e.g., 130 C. air for ten minutes.

A preferred process is to saturate the drawn tow with water, piddle it onto a continuous belt, subject to atmospheric steam for 1-4 minutes (which crimps the filaments), remove excess water by passing through rollers, cut into staple lengths and dry with 80-l30 C. air for 10-20 minutes.

Although this invention has been illustrated with dry spinning, it is, of course, applicable to filaments prepared by wet spinning, plasticized melt spinning, as described in U.S. Patent No. 2,706,674 issued to Rothrock on April 19, 1955, or melt spinning.

Although this invention has been illustrated by the use of side-by-side structures, a structure which has a core completely and eccentrically surrounded by a sheath is applicable. For example, a sheath of a copolymer made from acrylonitrile, methyl acrylate and potassium styrenesulfonate with monomer feed ratios of 93.5 5.96/ 0.54 was spun around a core of homopolymer of acrylonitrile using a spinneret similar to that shown in copending application 519,031, filed March 19, 1956, to I. Killian (plateau spinneret), now U.S. Patent 2,936,482. The sheath and eccentrically disposed core comprised 50% each of the filamentary volume. The 160 filament bundle of yarn was drawn 4 in 95 C. water. Upon boiling the drawn I yarns in water, crimped filaments with a reversible crimp were obtained. With this type of structure the component having the greater reversible length change is preferably spun as the sheath of the filaments.

The filaments of the above examples, and yarns produced therefrom, possess, in common with all the filaments of this invention, the characteristic of crimp reversibility, that is, the ability to return to the original crimp state spontaneously after having been treated with a swelling agent and after removal of the swelling agent follovnfng such treatment. The preferred system exhibiting this characteristic of crimp reversibility involves filaments which have been crimped by a suitable shrinking treatment and which, upon being swollen, lose a portion of the crimp. Such filaments may be woven or knitted, either in the potentially crimpable or in the crimped state, as continuous filaments or as staple fibers, and if woven or knitted in the uncrimped or potentially crimpable state, the'crimp may be developed in the fabric by treatment with a suitable shrinking agent. The crimped filaments of the fabric will, upon treatment with a swelling agent, as by aqueous treatment in the washing, scouring, dyeing, and other treatments normally applied to fabrics, move around or squirm during such treatments and, upon removal of the swelling agent, regain the lost crimp with the imparting of a fullness and highly increased covering power to the fabric. Not only is this of advantage in the type of fabric used for clothing, but it is of great importance in piled fabrics such as those used in carpets and upholstery, where the compacting of the fibers under compression incident to use, may be overcome by treatment with water, other swelling agent, or merely exposure to humid air to cause the fibers to squirm or work out of the compressed state, but upon drying, the fibers will again revert to their highly crimped and voluminous state prior to their having been compressed. Although the invention has, in its preferred form, been applied to filaments which lose at least a part of their crimp upon the swelling treatment, it is within the scope of this invention to utilize a reversible crimp wherein the crimped filaments actually gain additional crimp upon treatment with a swelling agent; in this case, also, the filaments squirm and work around with respect to each other upon treatment with a swelling agent and also upon removal of the swelling agent as by drying, thereby, because of the freedom of movement of the filaments even with increased crimp, insuring the imparting of increased fullness, bulk and covering power to the fabric.

The invention is particularly directed to filaments and yarns (i.e., bundles of filaments) having deniers of the magnitude used in textiles. It is preferred that the filaments of this invention have a denier of 1 to 10 (inclusive) and that the yarns of this invention have a denier of 30 to 8,000 (inclusive).

While the invention has been described in its preferred form with respect to filaments made by extrusion from round spinneret orifices, the orifices may be of a different shape, e.g., cruciform, square, triangular or slotted to 21 yield filaments having a cross-section corresponding generally to the shape of such holes, i.e., crossor star-shaped, square, triangular or elliptical (the shape imparted by a slotted or elongated rectangular spinning orifice).

Although the above description refers to the use of illustrate typical cross-sections of side-by-side composite filaments of this invention made in accordance with the above examples. FIGURE 6 of the drawings also illustrates typical cross-sections of side-by-sidefilaments of this invention produced when the spinning conditions are varied somewhat from those which tend to produce filaments having the cross-sections of FIGURES 4 and 5.

Since the invention is capable of considerable variation and modification, any departure from the above description which conforms to the spirit of the invention, is also intended to be included within the scope of the claims.

We claim:

1. A composite filament crimpable from the straight state upon relaxation by shrinking comprised of at least two polymeric components selected from the group consisting of addition polymers and polyesters, said polymeric components being eccentrically disposed towards each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, each of said components extending throughout the length of said filament, one of said components containing at least 30 milliequivalents per kilogram of polymer of ionizable groups chemically bonded to the polymer chain and a nonionic dispersed dye-enhancing modifier as a copolymerized element of said component, said groups being ionizable in a swelling agent for said component to provide a reversible length change in said component with said nonionic modifier enhancing the effect of said ionizable groups by increasing said reversible length change, one of said'oomponents having a shrinkability of at least 1% greater than,

any of said other components and one of said components having a reversiblelength change after' shrinkage evidenced by anincrease in'length of at least 0.05%

greater than anyof said other components when treated with said swelling agent with said component substantially returning to its original length upon removal of said swelling agent, said filament assuming a crimped state upon relaxation by shrinking and exhibiting crimp reversibility characterized by squirming of said filament upon treatment with and upon removal of said swelling agent after shrinking.

2. The filament of claim 1 in which said two filament components comprise vinyl polymers.

3. The filament of claim 1 in which said two filament components comprise acrylonitrile polymers.

4. The filament of claim 1 in which said two filament components comprise polyesters.

5 The filament of claim 4 wherein said polyesters are polyethylene terephthalate and said ionizable groups are provided by sodium 3,5-dicarbomethoxy)-benzenesulfonate.

-6. Fabrics comprising filaments of claim 4.

7. Fabrics comprising filaments of claim 1.

8. Fabrics comprising filaments of claim 1- in which said two filament components comprise acrylonitrile polymers.

9. The filament of claim 1 wherein said nonionic modi- 22 fier comprises at least 3% by weight of said one component.

10. The filament of claim 9 in which said two filament components comprise acrylonitrile polymers.

11. The filament of claim 10 wherein said nonionic modifier is methyl acrylate.

12. The filament of claim 11 wherein said ionizable groups are provided by sodium p-styrenesulfonate.

13. The filament of claim 10 wherein said nonionic modifier is vinyl acetate.

14. A composite filament crimpable from the straight state upon relaxation by shrinking comprised of two polymerie components selected from the group consisting of addition polymers and polyesters having an initial modulus at 25 C. in water of at least 10 grams per denier, said polymeric components being eccentrically disposed towards each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, each of said components extending throughout the'length of said filament, one of said components containing at least 30 milliequi'valents per kilogram of polymer of ionizable groups chemically bonded to the polymer chain and 3% of a nonionic dispersed dye-enhancing modifier as a copolymerized element of said component, said groups being ionizable in a swelling agent for said component to provide a reversible length change in said component with said nonionic modifier enhancing the effect of said ionizable groups by increasing said reversible length change, one of said components having a shrinkability of at least 1% greater than any of said other components and one of said components having a reversible length change after shrinkage evidenced by an increase in length of at least 0.10% greater than any of said other components when treated with said swelling agent with said component substantially returning to its original length upon removal of said swelling agent, said filament assuming a crimped state upon relaxation by shrinking and exhibiting crimp reversibility characterized by squirming of said filament upon treatment with and upon removal of said swelling agent after shrinking.

15. The filament of claim 14 in which said two filament components comprise acrylonitrile polymers.

16. The filament of claim 15 wherein said nonionic modifier is methyl acrylate.

References Cited in the file of this patent UNITED STATES PATENTS 2,234,763 Hoelkeskamp Mar. 11, 1941 2,287,099 Hardy et al. June 23, 1942 2,351,090 Alles June 13, 1944 2,428,046 Sisson et a1 Sept. 30, 1947 2,439,814 Sisson Apr. 20, 1948 2,439,815 Sisson Apr. 20, 1948 2,571,457 Ladisch Oct. 16, 1951 2,674,025 Ladisch Apr. 6, 1954 2,764,468 Hare Sept. 25, 1956 2,808,311 Hare Oct. 1, 1957 2,875,019 Spohn et al. Feb. 24, 1959 2,931,091 Breen Apr. 5, 1960 FOREIGN PATENTS 1,124,921 France July 9, 1956 514,638 Great Britain Nov. 14, 1939 562,555 Great Britain July 6, 1944 760,179 Great Britain Oct. 31, 1956 

1. A COMPOSITE FILAMENT CRIMPABLE FROM THE STRAIGHT STATE UPON RELAXATION BY SHRINKING COMPRISED OF AT LEAST TWO POLYMERIX COMPONENTS SELECTED FROM THE GROUP CONSISTING OF ADDITION POLYMERS AND POLYESTERS, SAID POLYMERIC COMPONENTS BEING ECCENTRICALLY DISPOSED TOWARDS EACH OTHER IN DISTINCT ZONES WITH ADJOINING SURFACES BEING IN INTIMATE ADHERING CONTACT WITH EACH OTHER, EACH OF SAID COMPONENTS EXTENDING THROUGHOUT THE LENGTH OF SAID FILAMENT, ONE OF SAID COMPONENTS CONTANNG AT LEAST 30 MILLIEQUIVALENTS PER KILOGRAM OF POLYMER OF IONIZABLE GROUPS CHEMICALLY BONDED TO THE POLYMER CHANIN AND A NONIONIC DISPERSED BYE-ENHANCING MODIFIER AS A COPOLYMERIZED ELEMENT OF SAID COMPONENT, SAID GROUPS BEING IONIZABLE IN A SWELLING AGENT FOR SAID COMPONENT TO PROVIDE A REVERSIBLE LENGTH CHANGE IN SAID OCMPONENT WITH SAID NONIONIC MODIFIER ENHANCING THE EFFET OF SAID IONIZABLE GROUPS BY INCREASING SAID REVERSIBLE LENGTH CHANGE, ONE OF SAID COMPONENTS HAVING A SHRINKABILITY OF AT LEAST 1% GREATER THEN 